spase://CNES/NumericalData/CDPP-AMDA/IMP-8/MIT/imp-mit-k0

The MIT Faraday cup experiment on IMP 8 measures currents from solar wind ions, and from these measurements we calculate the velocity, density, and temperature of the solar wind. The IMP 8 data files consist of fine resolution data (approximately 1 minute resolution). IMP 8 spins with a period of approximately 2.7s. The Faraday Cup (FC) instrument scans the solar wind distribution stepping through a contiguous set of energy windows, one step per spacecraft spin. The FC instrument divides the spin into thirty-two, 11.25 degree angular sectors and integrates the measured currents over different angular sectors depending upon the Mode in which the instrument is operating. The border between two of the 11.25 degree angular sectors lies on the Sun-spacecraft line. The FC sensor collector plate is divided into two, semi-circular halves; the division line is parallel to the spacecraft spin plane which is approximately parallel to the ecliptic plane. The split collector allow determination of the bulk plasma flow relative to the spin plane; North/South angles refer to flows coming from above or below the spin plane respectively (flows from the South are designated as having a positive N/S angle). The bulk flow angle in the spin plane is determined from the measurements of current vs. rotation angle. The currents telemetered to the ground are the sums of currents for the two half-collectors ("A" and "B") and, for the TMS and AQM modes, also the current for the half-collector "B". Electrons are measured except for the eight angles near the Sun. The experiment has two memories only one of which is operating perfectly. As a result, only every other TMS spectrum is usable, and the time between spectra is usually twice that that would be expected from the spacecraft spin rate. The bad half-memory also limits the energy windows that can be used in the other modes, since they require both memories to hold the data. On occasion, the data are read out rapidly enough by the spacecraft to allow repeated use of the good half-memory, and the time resolution in the TMS is approximately 32 seconds.